Can’t create a new XMLDB file

The Moodle XMLDB plugin does some checks of the db/ folder in your plugin to ensure it has read/write access before allowing certain permissions (e.g. create and load). If it doesn’t find this, the text will appear but it won’t be a hyperlink.

Have a look in admin/tool/xmldb/actions/main_view/main_view.class.php

For example for the create button it will have:

 // The create button
                if ($dbdir->path_exists &&
                    !file_exists($key . '/install.xml') &&
                    is_writeable($key)) {                                       

So the db directory needs to exist and be writable by the user running the Moodle instance (e.g. if using apache the user that apache runs as).